It has been known that seatbacks for vehicles, such as an automobile, which seatback is provided with a plurality of band-shaped antenna electrodes spaced in an up and down direction, for example as disclosed in Japanese Patent No. 3347069 (US6404074B2). A presence or absence of an occupant or a position of a head of an occupant is detected on the basis of a value of electric current supplied to these antenna electrodes.
Such back supporting portion is provided with a plurality of rectangular-shaped electrodes on which electric field is generated. Electric lines of force, which are not necessarily utilized for detecting an occupant, are emitted from these electrodes to surroundings and may badly influence on electronic applications such as audio equipments, radio equipments and so on. Besides, each back supporting portion is provided with several separated electrodes such that an initial capacity of the set of the electrodes is not determined until being assembled at the back supporting portion or the seatback. Therefore, fluctuations of the initial capacity of the electrode set are likely to be large. This may cause measuring or detecting within a wide measuring range and may deteriorate sensitivity for occupant detection.
The present invention has been made in view of the above circumstances, and provides a seat for a vehicle, which enables to detect an occupant while restraining detrimental effects to surroundings.